Cementing plug stop for well casings



Nov. 7, 1939. r R, Q BA ER ETAL 2.178.847

CEMENTING PLUG STOP FOR WELL CASINGS Filed March 20, 1959 2 Sheets-Sheet l Q; Q H

INVENTOR. REueE/v C. BAKER C'LA RENCE' E. BURT A TTORNEY C a caA/Q.% I

NOV. 7, 1939. R c, BAKER 51' CEMENTING PLUG STOP FOR WELL CASINGS Filed March 20, 1939 2 Sheets-Sheet 2 1 15.4 TTifi-E wliiiiii zlzg INVENTOR. Rsuazzv 6'. BA KER CLAPENCE E. .Bun n A'TTORNEYS.

Patented Nov. 7, 1939 UNITED STATES PATENT OFFICE 2,178,847 I w CEMENTING PLUG s'roP'FoRWELL CASINGS Reuben C. Baker, Coalinga, and Clarence E. Burt,

Los Angeles, Calif., assignors to Baker Oil Tools, Inc., Huntington Park, Calif., a corporation of California Application March 20,- 1939, Serial No.. 262,850

11Claims (01. 166-1) This invention relates generally to the cementing of deep well casings and is more particularly directed to a stop device capable of being incorporated in a well casing and of vfunctioning to arrest downward travel of an instrumentality employed in a cementing operation.

It is more or less a general practice in the cementing of well casings to incorporate in the casing string at a desired elevation, an abutment device serving as a stop-for arresting downward travel of a cementing plug, and to position such device within a coupling in the space between the opposed ends of two adjacent casing lengths so as to be clamped by said casing ends as the casin string is made up.

The usual method of cementing a string of casing in a well bore involves pumping a quantity of cement slurrydown the casing, around the casing shoe and up into the annular space outside the casing to obtain a water shut-off, and for this purpose the casing, at a suitable distance above the casing shoe, is provided with a stop means for arresting the cementing plug which is propelled by circulation fluid to drive the cement down the casing, the arresting of said plug at the completion of the cementing operation being evidenced at the well surface by an increase in the circulation gage pressure.

In many instances it is desired to place a batch of cement behind a casing at a higher level, to

protect or control a productive formation, or for other purposes, and insuch instances the casing is provided with an interior abutment or stop positioned below perforations or cement discharge ports through which the cement is to be forced into the space between the well casing and the well bore, the usual procedure being to place within the casing at the surface a lower bridging element or barrier plug followed by a measured quantity or batch of cement slurry and an upper plug, all of which will be driven down to the cementing station by fluid pumped into the casing above the upper plug. After the lower barrier plug contacts and is arrested by the abutmentor stop, the pump pressure then will be effective to continue the downward travel of the upper plug in relation to the arrested lower or barrier plug, and thus force the cementslurry through the perforations or cement discharge ports until the upper plug engages and is itself arrested by the then stationary barrier plug.

By those skilled in this art it is well understood that it requires great force to drive cement slurry down around a casing shoe and upwardly the required distance in the annular space between the casing and the well bore, or to squeeze a batch of cement from between an upper and a lower plug and through casing perforations or discharge ports and upwardly in said annular space.

It is also understood that, particularly in very deep wells, the abutment or stop employed to arrest a cementing plug must be of exceptionally sturdy construction to withstand the pressure involved, and, since the space available within a standard casing couplingbetween the ends of the adjacent casing lengths is relatively small and is closely maintained to a fixed standard, there is a well established limit to the pressure resisting strength of that type of stop device which is supported wholly by means projecting into said small space and secured in place only by the relatively thin walls of the adjacent casing lengths.

'It is, therefore, the principal object of the present invention to provide a stop device adapted to be disposed within a standard casing coupling and secured therein between adjacent casing lengths and which has incorporated in its structure a stop means adapted to be engaged by the object whose downward travel it is.designed to arrest and to be operated thereby to grippingly engage the interiorwall surface of the casing with a gripping force proportioned to the pressure load above said object and transfer to said wall surface the major portion of said load.

The invention is exemplified in the following description and illustrated by way of example in the accompanying drawings, in which:

Fig. lis a vertical section through the coupling and the end portions of two adjacent casing lengths, showing my improved stop device disposed therein with the parts in relative normal positions.

Fig. 2 is a similar section showing the device operated tocasing gripping condition by a cementing plug.

Fig. 3 is a bottom plan view taken on the line IIII1'I of Fig. 1.

Fig. 4 is a section, similar in character to Fig. 1, showing a modified embodiment of the invention.

Fig. 5 is a vertical section taken substantially on the line V--V of Fig. 6.

Fig. 6 is a bottom plan view taken on the line VI-VI of Fig. 4.

In the embodiment shown in Figs. 1, 2 and 3 of the drawings, the screw-threaded ends of the adjacent casing lengths A and B are connected by a standard screw-threaded casing coupling C which provides a medial interior space D between the opposed ends of said casing lengths.

The stop device E comprises an annular supporting member or flange ring ID, a plurality of casing gripping slips l I and a sl p expanding cone l2, said flange ring being adapted to be engaged upon the upper end of the casing length B within the space D as the casing string is being made up and to be retained in place by the lower end of the casing length A so as to dispose the casing slips II and associated expanding cone I2 above the flange ring In and within the lower end por-- tion of the casing length A.

We preferably employ four circularly spaced slips, each of which rests upon the flange ring I0 and is vreleasably connected to the tubular expanding cone I2 by means of one or more shear screws I3, the several shear screws retaining the slips in normal collapsed condition and supporting the cone in its uppermost position, as shown in Fig. l.

The expanding cone I2 is maintained axially disposed in relation to the supporting flange ring II! by a depending tubular skirt I I, which is slidable in the bore of said ring and is prevented from rotation therein by vertical exterior ribs I5 engaging within companion interior grooves I6 formed in the inner wall of said bore, the lower end of said skirt being provided with ears I I which carry transversely disposed stop pins I8 that project laterally beneath the lower surface of the flange ring Ill and serve to limit upward movement of the expanding cone. These stop pins are particularly intended to prevent upward displacement of the expanding cone during lowering of the casing through fluid contained in the well or by such back-pressures as may develop in the set casing, and also to prevent disarrangement of the parts during the making up of the casing string and to provide a preassembled stop' unit which may be shipped and handled without loss of or disarrangement of the parts comprising such unit.

With the stop unit assembled in the casing string as shown in Fig. 1, the cementing operation may be conducted until a cementing plug F engages the upper surface of the expanding cone I2 to drive said cone downwardly and shear the several shear screws I3 to release the slips I I and expand said slips outwardly to gripping engagement with the casing wall, as shown in Fig. 2.

It will be evident that as the pressure load transmitted to the expanding cone by the arrested cementing plug increases the expanded slips will gripthe casing wall with a force proportioned to said pressure load and will thus relieve the relatively weak flange ring of the major portion of the load.

In Figs. 4 to 6 of the drawings, there is disclosed a modified structure in which the flangering IIla and the several slips I la are combined to form an integral member 20 having a central vertical bore 2I which, as shown in Fig. 6, is preferably octagonal in cross-sectional contour and is formed to provide upwardly and outwardly tapered walls disposed for engagement with similarly tapered Walls of a tubular slip expanding cone I2a, said cone having a depending leg IIa carrying a stop pin or bolt I8a disposed below the lower end of the flange ring Illa and serving a purpose similar to that of the stop pins I8 of the previously de scribed device.

The wall of the member 20 is longitudinally slotted at circularly spaced intervals, preferably at the points of juncture of the several fiat sides of the octagonal bore 2I, to define the several slips I la, the upper portions of which are provided with external horizontally disposed gripping teeth or wickers 22. It will be noted that four slots 23 of those which define the slips are so shaped as to leave at their upper ends relatively small weak connecting bridges 24 and to leave at their lower ends relatively larger and stronger connecting bridges 25, while the four intermediate slots 26 are shaped in a reverse manner to leave relatively large strong connecting bridges 21 at their upper ends and relatively smaller and weaker connecting bridges 28 at their lower ends, the purpose of thus forming the several slots being to weaken the integral member 2Ilv at the smaller and weaker connecting bridges 24 and 28 respectively, which are at the opposite ends of the adjacent slots.

In use, the assembled unit E will be disposed in the casing as shown in Fig. 4 and when engaged by the cementing plug F, as shown in Fig. 5, the expanding cone I2a will exert an expanding force suflicient to rupture the several smaller and weaker'connecting bridges 24 and 28 (at points indicated by dotted lines 30 in Fig. 4) and effect expansion of the integral member 20 such as will cause the several slip sections IIa to engage and grip the casing walL said slips Ila then performing their load supporting function in the same manner as will the slips I I of the previously described device shown in Figs. 1 to 3.

It is to be understood that the several parts comprising the described stop units will be made I of easily drillable material so that they may be drilled up and circulated out of the casing after a cementing operation has been completed.

From the foregoing it will be evident that the present invention provides, in two forms, a simple and effective stop unit for well casing, which may safely be transported and handled without danger of disarrangement or loss of parts and which may be 'quickly and easily incorporated in a casing string. as it is made up,-without in any way modifying the standard casing lengths or couplings comprising such casing string, and which, when in use, will effectively transmit the pressure load applied thereto directly to the casing wall.

While the present invention is herein disclosed in its preferred forms it is to be understood that various changes may be made therein by those skilled in the art without departing from the spirit of the invention as defined in the appended claims.

Having thus described our invention, what we claim and desire to obtain by Letters Patent is:

1. In combination with a well casing, including a coupling joining two adjacent casing lengths, an annular supporting member disposed within said coupling and secured between the opposed ends of said adjacent casing lengths against longitudinal'displacement, and a normally ineffective casing gripping stop means carried by said sup porting member and disposed within said casing in position for engagement by an object adapted to be sent down the casing, said stop means being operable by said object to grip the inner surface of the casing wall to arrest downward travel of said object.

2. In combination with a well casing including a coupling joining two adjacent casing lengths, an annular supporting member disposed within said coupling and secured between the opposed ends of said adjacent casing lengths against longitudinal displacement, and a stop means carried by said supporting member and disposed within said casing and comprising normally ineffective casing gripping means and a'tubular stop member disposed for engagement by an object adapted to be sent down the casing, said stop member being operable by said object to engage said gripping means with the inner surface of the casing wall and arrest downward travel of said object.

3. In combination with a well casing including a coupling joining two adjacent casing lengths, a flange ring transversely disposed within said coupling and secured between the opposed ends of said adjacent casing lengths against longituand a tubular slip expanding stop member dis posed for engagement by an object adapted to be sent down the casing, said stop member being translatable by said object to expand said slips to gripping engagement with the inner surface of the casing wall and arrest downward travel of said object.

4. In combination with a well casing including a coupling joining two adjacent casing lengths, a flange ring transversely disposed within said coupling and secured between the opposed ends of said adjacent casing lengths against longitudinal displacement, and a stop means carried by said flange ring and disposed within the casing and comprising normally collapsed casing slips disposed within the upper casing length and a tubular longitudinally translatable slip expanding cone supported by and extending upwardly beyond said slips for engagement by a cementing plug adapted to be sent down the casing, said cone being downwardly translatable by said plug to expand said slips to gripping engagement with the inner surface of the casing wall and arrest downward travel of said plug.

5. In combination with a well casing including a coupling joining two adjacent casing lengths, a flange ring transversely disposed within said coupling and secured betweenthe opposed ends of said'adjacent casing lengths against longitudinal displacement, and a stop means carried by said flange ring and disposed within the casing and comprising normally collapsed casing slips radially slidable on said flange ring, and a longitudinally translatable slip expanding cone disposed within and extended upwardly beyond said slips for engagement by a cementing plug adapted to be sent down the casing, said cone being normally joined to and supported on the several slips by connecting means capable of being disabled by relative longitudinal movement between said cone and said slips, and being translatable downwardly by said plug to disable said connecting means and expand said slips to gripping engagement with the inner surface of the casing wall and arrest downward travel of said plug.

6. In combination with a well casing including a coupling joining two adjacent casing lengths, and a stop means disposed within said casing and comprising a tubular supporting member disposed within said casing and having a lateral external flange disposed within said coupling and secured between the opposed ends of said adjacent casing lengths against longitudinal displacement, said member having a toothed external surface and being longitudinally slotted at circularly spaced intervals to define circularly adjacent casing gripping slips and to define relatively fragile bridges normally connecting the adjacent slips and a slip expanding cone disposed within said slip member in position to be engaged and translated downwardly by a cement plug adapted to be sent down the casing, said cone functioning to rupture said fragile bridges and expand the toothed slips to gripping engagement with the inner surface of the casing wall and arrest downward travel of said plug.

7. In combination with a well casing including a coupling joining two adjacent casing lengths, an annular supporting member disposed within said coupling and secured between the opposed ends of said adjacent casing lengths against longitudinal displacement, and a normally ineffective casing gripping stop means carried by said supporting member and disposed within said casing in position for engagement by an object adapted to be sent down the casing, said stop means being operable by said object to grip the inner surface of the casing wall to arrest downward travel of said object and means preventing an appreciable upward displacement of said stop means relative to said supporting member.

8. In combination with a well casing including a coupling joining two adjacent casing lengths, a flange ring transversely disposed within said coupling and secured between the opposed ends of said adjacent casing lengths against longitudinal displacement, and a stop means carried by said flange ring and disposed within the casing and comprising normally collapsed casing slips disposed within the upper casing length and a tubular longitudinally translatable slip expanding cone supported by and extending upwardly beyond said slips for engagement by a cementing plug adapted to be sent down the casing, said cone being downwardly translatable by said plug to expand said slips to gripping engagement with the inner surface of the casing Wall and arrest downward travel of said plug and means preventing an appreciable upward displacement of said expanding cone relative to said flange ring.

9. A stop assembly adapted to be incorporated in a well casing including a coupling joining two adjacent casing lengths, said assembly comprising a supporting flange ring adapted to be disposed within said coupling and secured between the opposed ends of said adjacent casing lengths against longitudinal displacement, normally collapsed casing slips supported by said member and adapted to be inserted within the casing, a slip expanding cone normally joined to and supported on the several slips by connecting means capable of being disabled by relative longitudinal movement between said cone and said slips, and means maintaining the parts in assembled condition.

10. A stop assembly adapted to be incorporated in a well casing including a coupling joining two a tubular supporting member adapted to be disposed within said casing and having a lateral external flange adapted to be secured between the opposed ends of said adjacent casing lengths, said member having a toothed external surface and being longitudinally slotted at circularly spaced intervals to define circularly adjacent toothed casing gripping slips and to define relatively fragile bridges normally connecting the adjacent slips, a slip expanding cone disposed within said supporting member and adapted for longitudinal translation to rupture said fragile bridges and expand the toothed slips, and means maintaining the parts in assembled condition.

11. A stop assembly adapted to be incorporated in a well casing including a coupling joining two adjacent casing lengths, said assembly compris- 

